Originally Posted by w00zup!?
Just go to the store, try on a few helmets to get a sense of the sizes, and when you find something that you think fits you well shake your head a bit to see it ain't moving and fits tightly (yet comfortably)
Yeah, he made a good and *important* point. You want it to fit snug, but not tight enough to give you a headache. If you forsee wearing balaclava / face mask, wear it when you are trying the helment on. If you wear goggles, bring those too. Some helemts are not (really) compatable with goggles, others are. Any decent sales person should be able to help you out. And if you want to be sneaky, go try stuff on at a store, find your size, etc, and then try to score it from a close-out sale on-line. You can get some serious discounts that way.